1. Field of the Invention
The present invention relates to a wrist watch with hour and minute hands, i.e., analog-type watch, wherein at least one of the hands is in the form of a rotatable circular film.
The present invention also relates to an electrostatic shielding device in the analog-type watch.
2. Description of the Related Art
There has always been a demand for "slim", i.e., thin, wrist watches, particularly in the field of analog-type wrist watches (hereinafter, watch). The thinning of the thickness of a wrist watch can be realized by reducing the thickness of the movement of the watch and the distance between the outer glass and the dial. Many solutions to the problem of a reduction of the thickness of the movement have been proposed, but the distance, i.e., space, between the glass and the dial in which the hour hand and the minute hand are arranged is not easily decreased, since the hour hand and the minute hand must be spaced from each other an from the glass and the dial. Namely, if the hands come into contact with each other or with the dial or the glass during rotation of the hands, the hands may jam and become immovable, and eventually, the watch will stop. In particular, when the two hands collide, the rotation of the hands may come to a complete stop. Accordingly, the inevitable gaps between the minute hand and the hour hand, between the hands and the glass, and between the hands and the dial are an obstacle to a reduction of the total thickness of the watch.
Under these circumstances, it has been proposed to replace the conventional hands, which are, for example, in the form of needles or the like, with rotable circular films which have minute and hour hands depicted thereon, respectively. Wrist watches having minute and hour hands which are in the form of circular films are disclosed, for example, in Japanese Unexamined Patent Publication (Kokai) Nos. 56-673, 56-61675, 57-34480, and 56-27678.
The circular films and the case of the watch are usually made of a plastic material or the like, and the glass of the watch is usually made of glass material, but sometimes is also made of a plastic material.
In this kind of watch, which has hour and minute hands in the form of circular films, the problem of the production of static electricity has been newly raised. Namely, if the glass of the watch is subjected to friction by the clothes or hands of the wearer of the watch, static electricity accumulates in the glass.
In particular, static electricity is easily produced in relatively dry and cold weather. Due to this static electricity, the plastic circular film carrying the hour hand or the plastic circular film carrying the minute hand, or both, is (are) attracted by the electrostatic glass. As a result, the static electricity in the glass is directly transmitted to the circular films by contact between the circular films and the glass, or static electricity also accumulates in the circular films due to electrostatic induction. Consequently, the circular films are attracted to each other or are attracted by the glass or the dial, with the result that a motor which drives the circular films for rotation is subjected to an increasing load. This results in an increased consumption of electric power needed to drive the motor, and to a retardation of the rotation of the circular film(s) or a complete failure of the operation of the watch.
In addition to the foregoing, the circular films can become stuck together or to the glass or the dial due to a layer of water vapor therebetween, which can permeate into the watch if the watch is not completely waterproof.
The prior arts mentioned above do not teach any solution to the problem of static electricity. Also, the watches of the prior arts mentioned above have a complex construction, since the circular films are rotated by a movement which is separate from the circular films and which engages the outer peripheries of the circular films to cause rotation thereof.